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The controlled assembly of nanomaterials into desired architectures presents many opportunities; however, current preparations lack spatial precision and versatility in developing complex nano-architectures. Inspired by the amphiphilic nature of surfactants, we develop a facile approach to guide nanomaterial integration – spatial organization and distribution – in metal-organic frameworks (MOFs). Named surfactant tunable spatial architecture (STAR), the technology leverages the varied interactions of surfactants with nanoparticles and MOF constituents, respectively, to direct nanoparticle arrangement while molding the growing framework. By surfactant matching, the approach achieves not only tunable and precise integration of diverse nanomaterials in different MOF structures, but also fast and aqueous synthesis, in solution and on solid substrates. Employing the approach, we develop a dual-probe STAR that comprises peripheral working probes and central reference probes to achieve differential responsiveness to biomarkers. When applied for the direct profiling of clinical ascites, STAR reveals glycosylation signatures of extracellular vesicles and differentiates cancer patient prognosis., Current methods for controlled assembly of nanomaterials into desired architectures often lack the precision and versatility to develop complex architectures. Here the authors report STAR, surfactant tunable spatial architecture, to guide nanomaterial integration in metal-organic frameworks.

Accessible and adaptable nucleic acid diagnostics remains a critical challenge in managing the evolving COVID‐19 pandemic. Here, an integrated molecular nanotechnology that enables direct and programmable detection of SARS‐CoV‐2 RNA targets in native patient specimens is reported. Termed synergistic coupling of responsive equilibrium in enzymatic network (SCREEN), the technology leverages tunable, catalytic molecular nanostructures to establish an interconnected, collaborative architecture. SCREEN mimics the extraordinary organization and functionality of cellular signaling cascades. Through programmable enzyme–DNA nanostructures, SCREEN activates upon interaction with different RNA targets to initiate multi‐enzyme catalysis; through system‐wide favorable equilibrium shifting, SCREEN directly transduces a single target binding into an amplified electrical signal. To establish collaborative equilibrium coupling in the architecture, a computational model that simulates all reactions to predict overall performance and optimize assay configuration is developed. The developed platform achieves direct and sensitive RNA detection (approaching single‐copy detection), fast response (assay reaction is completed within 30 min at room temperature), and robust programmability (across different genetic loci of SARS‐CoV‐2). When clinically evaluated, the technology demonstrates robust and direct detection in clinical swab lysates to accurately diagnose COVID‐19 patients., A molecular nanotechnology is developed utilizing interconnected enzyme–DNA nanostructures to achieve cooperative multi‐enzyme catalysis. Through programmable nanostructures and favorable equilibrium coupling in the system architecture, the technology achieves sensitive and versatile detection for the direct measurement of SARS‐CoV‐2 RNA targets in native patient specimens (30 min at room temperature).

Biologically templated plasmonics enables simultaneous biophysical and biomolecular analysis of exosome biomarkers., Exosomes are nanoscale vesicles distinguished by characteristic biophysical and biomolecular features; current analytical approaches, however, remain univariate. Here, we develop a dedicated platform for multiparametric exosome analysis—through simultaneous biophysical and biomolecular evaluation of the same vesicles—directly in clinical biofluids. Termed templated plasmonics for exosomes, the technology leverages in situ growth of gold nanoshells on vesicles to achieve multiselectivity. For biophysical selectivity, the nanoshell formation is templated by and tuned to distinguish exosome dimensions. For biomolecular selectivity, the nanoshell plasmonics locally quenches fluorescent probes only if they are target-bound on the same vesicle. The technology thus achieves multiplexed analysis of diverse exosomal biomarkers (e.g., proteins and microRNAs) but remains unresponsive to nonvesicle biomarkers. When implemented on a microfluidic, smartphone-based sensor, the platform is rapid, sensitive, and wash-free. It not only distinguished biomarker organizational states in native clinical samples but also showed that the exosomal subpopulation could more accurately differentiate patient prognosis.

Accurate and accessible nucleic acid diagnostics is critical to reducing the spread of COVID-19 and resuming socioeconomic activities. Here, we present an integrated platform for the direct detection of SARS-CoV-2 RNA targets near patients. Termed electrochemical system integrating reconfigurable enzyme-DNA nanostructures (eSIREN), the technology leverages responsive molecular nanostructures and automated microfluidics to seamlessly transduce target-induced molecular activation into an enhanced electrochemical signal. Through responsive enzyme-DNA nanostructures, the technology establishes a molecular circuitry that directly recognizes specific RNA targets and catalytically enhances signaling; only upon target hybridization, the molecular nanostructures activate to liberate strong enzymatic activity and initiate cascading reactions. Through automated microfluidics, the system coordinates and interfaces the molecular circuitry with embedded electronics; its pressure actuation and liquid-guiding structures improve not only analytical performance but also automated implementation. The developed platform establishes a detection limit of 7 copies of RNA target per μl, operates against the complex biological background of native patient samples, and is completed in

Programmable Detection of SARS‐CoV‐2 In article number 2101155, Huilin Shao and co‐workers report the collaborative coupling of enzyme–DNA nanostructures to establish multi‐enzyme catalysis. Through programmable nanostructures and favorable equilibrium architecture, the technology achieves direct and sensitive detection of SARS‐CoV‐2 RNA in native patient samples, within 30 minutes at room temperature. [Image: see text]

DNA tetrahedron as the simplest 3D DNA nanostructure has been applied widely in biomedicine and biosensing. Herein, we design and fabricate a series of circular assemblies of DNA tetrahedron with high purity and decent yields. These circular nanostructures are confirmed by endonuclease digestion, gel electrophoresis and atomic force microscopy. Inspired by rotary protein motor, we demonstrate these circular architectures can serve as a stator for a rotary DNA motor to achieve the circular rotation. The DNA motor can rotate on the stators for several cycles, and the locomotion of the motor is monitored by the real-time fluorescent measurements. MOE (Min. of Education, S’pore) Published version

Exosomes have emerged as a promising biomarker. These vesicles abound in biofluids and harbor molecular constituents from their parent cells, thereby offering a minimally-invasive avenue for molecular analyses. Despite such clinical potential, routine exosomal analysis, particularly the protein assay, remains challenging, due to requirements for large sample volumes and extensive processing. We have been developing miniaturized systems to facilitate clinical exosome studies. These systems can be categorized into two components: microfluidics for sample preparation and analytical tools for protein analyses. In this report, we review a new assay platform, nano-plasmonic exosome (nPLEX), in which sensing is based on surface plasmon resonance to achieve label-free exosome detection. Looking forward, we also discuss some potential challenges and improvements in exosome studies.

Microvesicles (MVs) are an increasingly important source for biomarker discovery and clinical diagnostics. The small size of MVs and their presence in complex biological environment, however, pose technical challenges in sample preparation, particularly when sample volumes are small. We herein present an acoustic nanofilter system that size-specifically separates MVs in a continuous and contact-free manner. The separation uses ultrasound standing waves to exert differential acoustic force on MVs according to their size and density. By optimizing the design of the ultrasound transducers and underlying electronics, we were able to achieve a high separation yield and resolution. The "filter size-cutoff" can be controlled electronically in situ, which enables versatile MV-size selection. We applied the acoustic nanofilter to isolate nanoscale (200 nm) vesicles from cell culture media as well as MVs in stored red blood cell products. With the capacity for rapid and contact-free MV isolation, the developed system could become a versatile preparatory tool for MV analyses.

Circulating tumour cells (CTCs) and exosomes are promising circulating biomarkers. They exist in easily accessible blood and carry large diversity of molecular information. As such, they can be easily and repeatedly obtained for minimally invasive cancer diagnosis and monitoring. Because of their intrinsic differences in counts, size and molecular contents, CTCs and exosomes pose unique sets of technical challenges for clinical translation–CTCs are rare whereas exosomes are small. Novel technologies are underway to overcome these specific challenges to fully harness the clinical potential of these circulating biomarkers. Herein, we will overview the characteristics of CTCs and exosomes as valuable circulating biomarkers and their associated technical challenges for clinical adaptation. Specifically, we will describe emerging technologies that have been developed to address these technical obstacles and the unique clinical opportunities enabled by technological innovations.

Magnetic relaxation switching (MRSw) assays that employ target-induced aggregation (or disaggregation) of magnetic nanoparticles (MNPs) can be used to detect a wide range of biomolecules. The precise working mechanisms, however, remain poorly understood, often leading to confounding interpretation. We herein present a systematic and comprehensive characterization of MRSw sensing. By using different types of MNPs with varying physical properties, we analyzed the nature and transverse relaxation modes for MRSw detection. The study found that clustered MNPs are universally in a diffusion-limited fractal state (dimension of ~2.4). Importantly, a new model for transverse relaxation was constructed, that accurately recapitulates observed MRSw phenomena, and predicts the MRSw detection sensitivities and dynamic ranges.

Sensitive and quantitative measurements of clinically relevant protein biomarkers, pathogens and cells in biological samples would be invaluable for disease diagnosis, monitoring of malignancy, and for evaluating therapy efficacy. Biosensing strategies using magnetic nanoparticles (MNPs) have recently received considerable attention, since they offer unique advantages over traditional detection methods. Specifically, because biological samples have negligible magnetic background, MNPs can be used to obtain highly sensitive measurements in minimally processed samples. This review focuses on the use of MNPs for in vitro detection of cellular biomarkers based on nuclear magnetic resonance (NMR) effects. This detection platform, termed diagnostic magnetic resonance (DMR), exploits MNPs as proximity sensors to modulate the spin-spin relaxation time of water molecules surrounding the molecularly-targeted nanoparticles. With new developments such as more effective MNP biosensors, advanced conjugational strategies, and highly sensitive miniaturized NMR systems, the DMR detection capabilities have been considerably improved. These developments have also enabled parallel and rapid measurements from small sample volumes and on a wide range of targets, including whole cells, proteins, DNA/mRNA, metabolites, drugs, viruses and bacteria. The DMR platform thus makes a robust and easy-to-use sensor system with broad applications in biomedicine, as well as clinical utility in point-of-care settings.

Biocompatible magnetic nanoparticles (MNPs) that are both stable and amenable to chemical modification with targeting ligands continue to emerge as important materials in biomedical research.[1–5] MNPs provide an efficient contrast mechanism for biological targets; as most biological samples have intrinsically low magnetic susceptibility, only MNP-labeled objects will respond to external magnetic stimuli. Such properties have led to the widespread use of MNPs, for example, in cell sorting and bioseparation,[6, 7] medical diagnosis,[8–10] imaging,[11–14] and therapeutics.[15, 16]

Magnetic nanoparticles (MNPs) with high magnetic moments and very small size are under active development, since such materials have growing uses in biotechnology and medicine.[1] Ferromagnetic metals, rather than their corresponding oxides, have been suggested as an ideal constituent for MNPs for their superior magnetization.[2] Unfortunately, monometallic MNPs typically require protective layers to prevent progressive oxidation. To date, however, most core/shell approaches have yielded suboptimal magnetization, as the shell was formed either by artificially oxidizing the core[3,4] or by coating it with non-magnetic materials.[5]

Rapid and accurate measurements of protein biomarkers, pathogens and cells in biological samples could provide useful information for early disease diagnosis, treatment monitoring, and design of personalized medicine. In general, biological samples have only negligible magnetic susceptibility. Thus, using magnetic nanoparticles for biosensing not only enhances sensitivity but also effectively reduces sample preparation needs. This review focuses on the use of magnetic nanoparticles for in vitro detection of biomolecules and cells based on magnetic resonance effects. This detection platform, termed diagnostic magnetic resonance (DMR), exploits magnetic nanoparticles as proximity sensors, which modulate the spin–spin relaxation time of water molecules surrounding molecularly-targeted nanoparticles. By developing more effective magnetic nanoparticle biosensors, DMR detection limits for various target moieties have been considerably improved over the last few years. Already, a library of magnetic nanoparticles has been developed, in which a wide range of targets, including DNA/mRNA, proteins, small molecules/drugs, bacteria, and tumor cells, have been quantified. More recently, the capabilities of DMR technology have been further advanced with new developments such as miniaturized nuclear magnetic resonance detectors, better magnetic nanoparticles and novel conjugational methods. These developments have enabled parallel and sensitive measurements to be made from small volume samples. Thus, the DMR technology is a highly attractive platform for portable, low-cost, and efficient biomolecular detection within a biomedical setting.

During the course of their lifespan, erythrocytes actively shed phospholipid-bound microvesicles (MVs). In stored blood, the number of these erythrocyte-derived MVs has been observed to increase over time, suggesting their potential value as a quality metric for blood products. The lack of sensitive, standardized MV assays, however, poses a significant barrier to implementing MV analyses into clinical settings. Here, we report on a new nanotechnology platform capable of rapid and sensitive MV detection in packed red blood cell (pRBC) units. A filter-assisted microfluidic device was designed to enrich MVs directly from pRBC units, and label them with target-specific magnetic nanoparticles. Subsequent detection using a miniaturized nuclear magnetic resonance system enabled accurate MV quantification as well as the detection of key molecular markers (CD44, CD47, CD55). When the developed platform was applied, MVs in stored blood units could also be monitored longitudinally. Our results showed that MV counts increase over time and, thus, could serve as an effective metric of blood aging. Furthermore, our studies found that MVs have the capacity to generate oxidative stress and consume nitric oxide. By advancing our understanding of MV biology, we expect that the developed platform will lead to improved blood product quality and transfusion safety.

Accurate detection and profiling of circulating tumor cells (CTCs) is a highly sought after technology to improve cancer management. Such “liquid biopsies” could offer a non-invasive, repeatable window into each patient’s tumor, facilitating early cancer diagnosis and treatment monitoring. The rarity of CTCs, approximated at 1 CTC for every billion peripheral blood cells, however, poses significant challenges to sensitive and reliable detection. We have recently developed a new biosensor platform, namely a micro-nuclear magnetic resonance (µNMR). Through the synergistic integration of microfabrication, nanosensors, and novel chemistries, the µNMR platform offers high detection sensitivity and point-of-care operation, overcoming technical barriers in CTC research. We herein review the µNMR technology with emphasis on its application on CTC detection. Recent advances in the sensing technology will be summarized, followed by the description on the dynamic interplay between preclinical and clinical CTC studies.

For the sensitive and quantitative measurement of protein biomarkers, pathogens, and cells in clinical samples, magnetic nanoparticles (MNPs) offer unique advantages over traditional detection methods. Specifically, due to the inherently negligible magnetic background of biological material, MNPs can be used to obtain highly sensitive measurements in minimally processed samples. Our detection platform, termed diagnostic magnetic resonance (DMR), exploits MNPs to modulate the nuclear magnetic spin-spin relaxation time of water. Here, we review work done by our group to develop more effective MNP biosensors, advanced conjugational strategies to target the MNPs to molecular targets, and highly sensitive miniaturized NMR systems. We demonstrate this platform as a robust and easy-to-use system for the detection of a wide range of targets in clinical settings including whole cells, proteins, DNA/mRNA, metabolites, drugs, viruses, and bacteria.

Magnetic biosensors, based on nanomaterials and miniature electronics, have emerged as a powerful diagnostic platform. Benefiting from the inherently negligible magnetic background of biological objects, magnetic detection is highly selective even in complex biological media. The sensing thus requires minimal sample purification and yet achieves a high signal-to-background contrast. Moreover, magnetic sensors are also well-suited for miniaturization to match the size of biological targets, which enables sensitive detection of rare cells and small amounts of molecular markers. We herein summarize recent advances in magnetic sensing technologies, with an emphasis on clinical applications in point-of-care settings. Key components of sensors, including magnetic nanomaterials, labeling strategies and magnetometry, are reviewed.

We show the anisotropic selective growth of gold particles onto various nanomaterials to form heterodimers, tadpole-like and necklace-like hybrid structures via simple nucleation. The morphology of these hybrid nanostructures can be easily controlled. Necklace-like Pt–Au nanostructures demonstrated high stabilities as electrocatalysts for oxygen-reduction reaction.